Intracorporal injection of hSlo cDNA restores erectile capacity in STZ-diabetic F-344 rats in vivo

The ability of gene transfer with the poreforming subunit of the human maxi-K channel ( hSlo) to ameliorate the decline in erectile capacity commensurate with 12 - 24 wk of streptozotocin (STZ)-diabetes was examined in 181 Fischer-344 rats. A 2-mo period of STZ-diabetes was induced before gene transfer, and erectile capacity was evaluated by measuring the intracavernous pressure response (ICP) to cavernous nerve (CN) stimulation ( ranging from 0.5 to 10 mA). In the first series of experiments, ANOVA revealed increased CN-stimulated ICP responses at 1 and 2 mo postinjection of 100 mug pcDNA-hSlo compared with control values. A second series of experiments further examined the dose dependence and duration of gene transfer. The ICP response to submaximal ( 0.5 mA) and maximal ( 10 mA) nerve stimulation was evaluated 3 or 4 mo postinjection of a single dose of pcDNA-hSlo ranging from 10 to 1,000 mug. ANOVA again revealed that hSlo overexpression was associated with increased CN-stimulated ICP responses compared with responses in corresponding control animals. Histological studies revealed no immune response to the presence of hSlo. PCR analysis documented that expression of both plasmid and transcript were largely confined to the corporal tissue. In the third series of pharmacological experiments, hSlo gene transfer in vivo was associated with iberiotoxin-sensitive relaxation responses to sodium nitroprusside in corporal tissue strips in vitro. The latter data indicate that gene transfer produces functional maxi-K channels that participate in the modulation of corporal smooth muscle cell tone. Taken together, these observations suggest a fundamental diabetes-related change in corporal myocyte maxi-K channel regulation, expression, or function that may be corrected by expression of recombinant hSlo.